71 Demon Vinyl Top Trim Replacement

Unfortunately that clip is still in place so somehow I will need to remove it before i could attempt that which means i might have to take the headliner off or undo it from that area which is what I'm trying to avoid. I might try turning the clip to try and unscrew it from the outside but i think it would just spin and not loosen up the nut. I'm assuming since the other clips are plastic that this is the only one to make sure the trim piece stays in place so I'm assuming you have to tighten the nut on the inside.

I bought the car back in 81 and had it ever since. Had an engine vibration that keeps breaking the flexplate to the transmission so i parked it after about 5 years and then of course life happens and never had time or money for it but now I've been saving up my pennies(more like Benjamins) and I'm going through the whole thing. It's a Demon 340 Green Go with a black vinyl top, side stripes, taillight stripe and hood stripes with the hood scoops. It had A/C but the original owner took it all off to race it back then so I want to find all the A/C parts so i can enjoy the summers in it. Unfortunately the fender tag was long gone before i got it and no broadcast sheet inside (made in LA) which sucks because it has a lot of options on it.
Hello again, by chance is the last numbers on the vin 870 ? Possible that was my old car anyhow just curious now..thanks.
Looking for info